Sheet drying apparatus

ABSTRACT

Sheet material, such as photographic film, may be dried efficiently in an apparatus comprising A DRYING CHAMBER, HAVING FIRST AND SECOND PLENUMS, EACH OF SAID PLENUMS HAVING AN ARRAY OF NOZZLES FOR DIRECTING HIGH VELOCITY AIR AT THE RESPECTIVELY OPPOSITE SHEET SURFACES, FIRST AND SECOND SETS OF CONVEYING ROLLS ARRANGED SO AS TO PROVIDE A PATH FOR SHEET MATERIAL BETWEEN THE RESPECTIVE ARRAYS OF NOZZLES OF SAID PLENUMS AND SPACED SO AS TO CONTACT SHEET MATERIAL MOVING THROUGH SAID PATH, AND A PLURALITY OF FILAMENTARY GUIDES ON AT LEAST ONE SIDE OF SAID PATH.

United States Patent [1 1 Crowell 1 March 6, 1973 [541 SHEET DRYINGAPPARATUS 3,364,594 1/1968 Gruver ..34/162 [75] Inventor: i Arnold Crowd], wllmmgton Prima y Examiner-Carroll B. Dority, .lr.

, e i Attorney-William R. Moser [73] Assignee: E. I. du Pont de Nemours and Com- 1 pany, Wilmington, Del. [57] ABSTRACT [22] Filed: May 7, 1971 Sheet material, such as photographic film, may be pp No: 141,190 dned effic1ently 1n an apparatus comprising U.S. C1 ..'.....34/l56, 34/155 a drying chamber, having first and second plenums, each of said plenums having an array of nozzles for [52] directin hi h velocit air at the res ectivel 0 osite 51 Int. Cl ..F26b 13/00 sheet i i y p y pp [58] Field of Search ...34/l55, 156, 162, 160

first and second sets of conveying rolls arranged so as [56] References Cited to provide a path for sheet material between the respective arrays of nozzles of said plenums and v UNITEDYSTATES PATENTS spaced so as to contact sheet material moving-through 3,579,853 5 1971 Martino ..34/160 path and 3,199,213 8/1965 Milligan et 211...; ..34/160 X a plurality of filamentary guides on at least one side of 3,071,866 1/1963 Mangus ..34/155 X id th 3,140,157 7/1964 Fleissner et al.... ..34/l60 X 3,330,189 7/1967 Vil ..34/155 X 14 Claims, 5 Drawing Figures I 1 ll 32 I4 28 l2""' 22 13 l g 3 IO m E ii J m\\\\ m; =2;

INVENTOR JOHN ARNOLD CROWELL BY ATTORNEY PAIUHLUW 61m 3,718,983

SHEET'ZDF 3 FIG- xi 1 INVENTOR JOHN ARNOLD CROWELL ATTORNEY PATHHHJ 75 SHEET 30F 3 INVENTOR JOHN ARNOLD CROWELL ATTORNEY BACKGROUND OF THE INVENTION This invention relates to a drying apparatus for the removal of moisture from a web or sheet such as coated paper or film. It is particularly useful in the continuous processing of photographic film or paper.

Apparatus for drying sheet material, such as those disclosed in U.S. Pats. Nos. 3,041,729; 3,181,250, 3,308,555; and 3,548,512 generally operate using very high temperatures or conveying means that may abrade or damage the sheet material, making them unacceptable for use as compact processing apparatus for photographic film or paper. For this use, it is necessary to provide a dryer having a short drying chamber and conveying means that will not damage the material to be dried. Dryers having short drying chambers usually require the use of elevated temperatures to remove the moisture during a short residence time. Such elevated temperatures, in conjunction with the conveying means, often result in damage to the emulsion coating of photographic films. Use of high air velocities can often result in damage to the film or jamming of the apparatus due to improper support by the conveying.

means, and the flow path of the air may result in uneven drying.

SUMMARY OF THE INVENTION It has been found that the apparatus of the'invention enables the efficient and uniform removal of moisture from a web or sheet of coated film or paper over a short drying path without damaging the coated surface thereof. The useof very high temperature air may be avoided, and it is possible to use high flow rates of the drying medium (e.g., air) without the film or paper becoming caught in the conveying means and causing jamming.

- These improvements over the prior art are achieved by a drying apparatus comprising a dryingchamber having first and second plenums,

each of said plenums having an array of nozzles for directing high velocity air at the respectively opposite sheet surfaces,

.' first and second sets of conveying rolls arranged so as to provide a path for sheet material between the respective arrays of nozzles of said plenums and spaced so as to contact sheet material moving through said path, and

a plurality of filamentary guides on at least one side of said path.

The drying apparatus is particularly useful for receiving sheets or webs of photographic material from other photographic processing apparatus such as described in assignees U.S. application Ser. No. 748,101, Casey,

' filed July 26, 1968 now U.S.Pat. No. 3,589,263 issued June 29, 1971, and assignees copending U.S. application, Ser. No. 886,618, filed Dec. 19, 1969 now U.S. Pat. No. 3,635,144 issued Jan. 8, I972.

BRIEF DESCRIPTION or Tl-IE DRAWINGS FIG. 1 is a side elevation of one embodiment of the dryer in section.

FIG. 2 is a rear elevation in partial section of the lower portion of the dryer depicted in FIG. 1.

FIG. 3 is a side elevation in section of an alternate embodiment of the dryer.

FIG. 4 is a side elevation in cross-section of one of its nozzles.

FIG. 5 is a partial plan view showing an operable layout and spacing relationship of adjacent nozzles.

DETAILED DESCRIPTION OF THE INVENTION The sheet dryer ofthe invention is particularly suited for removal of moisture from a web or sheet of coated film or paper by virtue of its unique construction employing filamentary guides adjacent the path for the sheet material to be dried. In combination with the opposing nozzles and conveying rolls, the said guides permit sheet material to be moved through a path containing highly turbulent air from the nozzles without becoming caught in the nozzles or rolls. The apparatus satisfies another important requirement in accomplishing efficient drying without abrasion or damage to the sheet being dried. The apparatus is therefore particularly suitable for drying photographic films after processing, since it does not damage the emulsion coating thereon.

The first and second sets of conveying rolls are disposed so as to define a sheet material path therebetween. The sheet material passing through the dryer is therefore contacted on both surfaces by the rolls that define the sheet material path.

The filamentary guides are disposed substantially parallel to this sheet material path and, preferably, comprise two sets of stationary guides on opposite sides of the path, as shown in FIGS. 1 and 3. It is further preferred that these sets of guides form planes which are parallel to each other and to the sheet material path and are spaced no more than 0.5 inch apart. The dryer may, however, have filamentary guides ononly one side of the sheet material path, in which case a greater number of nozzles or greater air flow rate may be employed on the side having no filamentary guides, so that the sheet material tends to slide along the one set of filamentary guides as it passes through the dryer. In an embodiment wherein the conveying rolls have circumferential grooves, the filamentary guides pass through the grooves so as to provide guide means which can confine the sheet material within the sheet material path upto the point of contact with a conveying roll and from the point where contact between the sheet material and roll is lost at the other side of the. roll. The use of filamentary guides in the dryer, as described, accomplishes the guiding function with a minimum of interference withthe air from the nozzles, thus promoting efficient and uniform drying. The small size of the filaments permits the grooves in the rolls to be of a correspondingly small size, thus minimizing escape of air from the drying chamber.

The first and second sets of conveying rolls may consist of pairs of entrance and exit nip rolls only, as shown in FIG. 1, or additional rolls may be present, as shown in FIG. 3. The nip rolls preferably have surfaces of resilient polymeric material, which is resistant to corro sion and does not damage the sheet material.

The drying chamber, which contains the nozzle arrays between which the sheet material passes, must be long enough to allow sufiicient drying of the sheet material. The conveying rolls may be located either inside or outside the drying chamber, or both. Preferably, they are inside as illustrated by FIGS. 1 and 3. The dryer may be disposed vertically, horizontally as shown in FIG. I, or at an angle to the horizontal as shown in FIG. 3.

The invention will be better understood by specific reference to the drawings, which are provided to exemplify but not limit the invention.

The side elevation of FIG. 1 illustrates the embodiment in which the conveying rolls comprise coacting exit rolls 10, and entrance rolls 12, 12' inside the drying chamber 14. These rolls have surfaces of resilient, polymeric material l3, 13'. The upper 16 and lower 18 plenums are supplied with forced air, and the same exits through the upper 20 and lower 22 nozzles which are directed toward the center of the drying chamber. The sheet material path 24 in the center of the drying chamber and between the nozzles is shown with upper 26 and lower 28 filamentary guides, which are parallel to each other and to the sheet material path. The filamentary guides are anchored at one end to support members 30, 32 and are fastened at the other end to tension springs 34, 36. The filamentary guides, as shown, pass through grooves in. the exit rolls only. The entrance rolls may, however, be provided with circumferential grooves and the filamentary guides anchored so as to pass through the grooves of the entrance rolls also.

Other components of the drying apparatus, not shown, include a suitable housing, means for supplying air to the upper and lower plenums which may comprise a blower and ducts for recirculating air from the drying chamber to the blower. Baffle means for regulating the amount of air removed in excess of normal leakage from the dryer and for controlling the amount of make-up air drawn from the surrounding atmosphere, may also be provided. A heater, temperature sensor, and electrical controls are provided to heat the air used for drying but to keep it below a temperature that will cause damage to the sheet material.

FIG. 2 is a rear elevation of the dryer in partial section showing the lower exit roll 10, the circumferential grooves 38 therein, and a chain drive 40. The chain drive may be actuated by a separate electric motor, not shown, or in conjunction with other processing apparatus. The lower filamentary guide tension springs 36 and air supply duct 42 for the lower plenum 18 are also shown. The air supply duct is connected to the plenum by a rubber boot 19 or other suitable means.

FIG. 3 is an alternate embodiment of the dryer having a plurality of alternate upper 44 and lower 46 conveying rolls in cooperation with opposing arrays of air nozzles. The upper rolls are spaced from the lower rolls so that the sheet material may pass through the dryer flat, without bending, and still be engaged by the upper and lower rolls. Alternatively, the rolls may be spaced closer together so that the sheet must undulate as it passes through the dryer, thus providing firmer contact between the rolls and sheet material. In the illustrated embodiment of FIG. 3, the dryer is disposed at an angle to the horizontal. Upper 26 and lower 28 sets of filamentary guides are shown, but it is possible to use only one set, as pointed out above, since the additional conveying rolls assist in guiding the sheet material. Where two sets of filamentary guides are used, as shown, they should be no more than-0.5 inch apart and preferably no more than 0.25 inch apart.

FIGS. 4 and 5 show a preferred nozzle cross-section and a nozzle layout, respectively. Although the nozzles may be disposed in rows and columns perpendicular and parallel respectively to the direction of travel of the sheet material 24, it is preferred to dispose the columns askew to said path by an angle 4). A preferred value for d) is 10 for a nozzle array havingten rows or less, and 7 for a nozzle array having greaterthan ten rows. A preferred spacing L for adjacent nozzles in a row is 5 times the inside diameter d of the discharge end of the nozzle. A preferred spacing L for adjacent rows of nozzles is 0.8 times spacing L The diameter, d, is determined by the relationship:

d= 4e/45001m'. I

where d is the inside diameter of the discharge end of the nozzle in feet, 9 is the total air flow desired through the array in cubic feet per minute and n' is thenumber of nozzles per array. Although the nozzles can be formed in various configurations, it is preferred to form them in three frustoconical sections or acceleration zones I, II, and III defined by wall tapers B B and B Zone I has the largest diameter and is located at the base of the nozzle. It is a non-critical acceleration zone, and its opposing walls may be parallel or slightly tapered. Wall taper B may be from 0-4 and is preferably about 3. Zone II is an intermediate section I located between zones I and III. It is the critical acceleration zone, and its opposing walls are tapered to bring flow to 4,000 to 5,000 linear feet per minute by a l520 wall taper B over a length of 0.6 to 0.7 inch. A preferred wall taper B is about 15. Zone III is the nozzle section of smallest diameter and is located at the discharge end of the nozzle. It is a non-critical acceleration zone, and its opposing walls may be parallel or slightly tapered. Wall taper 8,, may be from 0-4 and is preferably about 3.

The preferred distance from the discharge opening of the nozzle to the sheet material path is 0.5 inch and a range of distance that has been found suitable is 0.25 to 0.75 inch. Although the conical nozzle is preferred, elliptical nozzles and other nozzle configurations may be suitable for practice of the invention. Preferred lengths for zone I and zone III are 0.9 and 0.2 inch, respectively, although these lengths may be varied considerably in the practice of the invention.

The 3 wall taper of zone I and zone III is preferred as it provides a large cross-sectional flow area between adjacent rows of nozzles and efficient exhaust air flow from the drying chamber.

Various parts of the apparatus can be made of stain less steel, aluminum, galvanized sheet metal or noncorrosive metal alloy, or made of suitable resins or polymers, e.g., phenol-formaldehyde resins, polyethylene, etc., that are resistant to heat and chemicals.

In particular, the first and second nozzle arrays can be vacuum molded from acrylic resin or other plastic material or sheets, and reinforced, if necessary, to provide the desired rigidity.

The filamentary guides may be made of any suitable wire, cable, or strand of small circular cross-section no more than 0.10 inch in diameter. A diameter of 0.006 to 0.06 inch is preferred. Monofilament nylon-line or metal wire with a plastic coating are particularly suitable materials.

The advantages of this invention include simplicity and dependability. Other advantages are that it uses a high volume of air and may operate at lower temperatures, e.g., ambient or room temperature to 150F. depending on the particular material to be dried, than other dryers.

In operation, the dryer may receive a web or sheet of processed photographic film either manually or automatically from other photographic processing apthe drying chamber and discharge it from the drying I apparatus. A rate of travel of the sheet material through the dryer of 5-10 feet/min., air flow rates of 600-1000 cubic feet/min., and air temperatures of 95135bLF. have been found suitable in useful embodiments of the dryer. From about 170 to about 420 nozzles per set have been employed for the upper and lower sets of nozzles. Drying chambers from 10 to 16 inches in length have been used. Moisture-removal rates of about 13 lb. of water/hour been achieved with such apparatus even under adverse conditions. These details of operation and design may, of course, be varied considerably in the practice of the invention.

lclaim: l. A sheet drying apparatus comprising a drying chamber having first and second plenums, each of said plenums having an array of nozzles for directing high velocity air at the respectively opposite sheet surfaces, said nozzles being comprised of at least two frusto-conical sections, the largest section being located at the base of the nozzle and having a wall taper of not more than 4, and the second section having a wall taper of l5-20, said nozzles being disposed in adjacent rows, the space L between adjacent nozzles within a row being no more than about 5 times the inside diameter of the discharge end of the nozzle, and the space L, between adjacent rows of nozzles being no more than about 0.8 times L first and second sets of conveying rolls arranged so as to provide a path for sheet material between the respective arrays of nozzles of said plenums and spaced so as to contact sheet material moving through said path, and a plurality of filamentary guides for said sheet material on at least one side of said path. 2. The apparatus of claim 1, at least one of said conveying rolls being driven.

3.- The apparatus of claim 2, said filamentary guides having a diameter of no more than 0.10 inch.

4. The apparatus of claim 3, said filamentary guides being substantially parallel to said path.

5. The apparatus of claim 4, at least one of said conveying rolls having a plurality of circumferential grooves at spaced intervals along its length, said filamentary guides passing through the portions of said grooves nearest said path.

6. The apparatus of claim 5, said first and second conveying rolls being located at spaced intervals throughout the length of said path.

7. The apparatus of claim 6, the filamentary guides having surfaces of polymeric material, being connected to spring tensioning means, and being located in two planes t at are parallel to each other and to said path and are no more than 0.5 inch apart, one ofsaid planes being on the bottom of said path, the other of said planes being on the top of said path.

8. The apparatus of claim 7 having at least one pair of coacting drive rolls, at least one of which has a surface of resilient polymeric material.

9. The apparatus of claim 8, said nozzles having three frusto-conical sections, the section of smallest diameter being located at the discharge end of the nozzle and having a wall taper of not more than 4, the intermediate section-having a wall taper of l5-20, and the largest section being located at the base of the nozzle and having a wall taper of not more than 4.

10. The apparatus of claim 3, said conveying rolls comprising two pairs of coacting drive rolls, one pair being located at the entrance of said drying chamber, the other pair being located at the exit of said drying chamber.

11. The apparatus of claim 10, at least one of said drive rolls having circumferential grooves at spaced intervals along its length, said filamentary guides being parallel to said path and passing through the portions of said grooves nearest said path.

12. The apparatus of claim 1 l, the filamentary guides having surfaces of polymeric material, being connected to spring tensioning means, and being located in two planes that are parallel to each other and to said path and are no more than'0.5 inch apart, one of said planes being on the bottom of said path, the other of said planes being on the top of said path.

13. The apparatus of claim 12, at least one of said coacting drive rolls having a surface of resilient, polymeric material.

14. The apparatus of claim 13, said nozzles having three frusto-conical sections, the section of smallest diameter being located at the discharge end of the nozzle and having a wall taper of no more than 4, the intermediate section having a wall taper of l5-20, and the largest section being located at the base of the nozzle and having a wall taper of not more than 4. 

1. A sheet drying apparatus comprising a drying chamber having first and second plenums, each of said plenums having an array of nozzles for directing high velocity air at the respectively opposite sheet surfaces, said nozzles being comprised of at least two frusto-conical sections, the largest section being located at the base of the nozzle and having a wall taper of not more than 4*, and the second section having a wall taper of 15*-20*, said nozzles being disposed in adjacent rows, the space L1, between adjacent nozzles within a row being no more than about 5 times the inside diameter of the discharge end of the nozzle, and the space L2 between adjacent rows of nozzles being no more than about 0.8 times L1, first and second sets of conveying rolls arranged so as to provide a path for sheet material between the respective arrays of nozzles of said plenums and spaced so as to contact sheet material moving through said path, and a plurality of filamentary guides for said sheet material on at least one side of said path.
 1. A sheet drying apparatus comprising a drying chamber having first and second plenums, each of said plenums having an array of nozzles for directing high velocity air at the respectively opposite sheet surfaces, said nozzles being comprised of at least two frusto-conical sections, the largest section being located at the base of the nozzle and having a wall taper of not more than 4*, and the second section having a wall taper of 15*-20*, said nozzles being disposed in adjacent rows, the space L1, between adjacent nozzles within a row being no more than about 5 times the inside diameter of the discharge end of the nozzle, and the space L2 between adjacent rows of nozzles being no more than about 0.8 times L1, first and second sets of conveying rolls arranged so as to provide a path for sheet material between the respective arrays of nozzles of said plenums and spaced so as to contact sheet material moving through said path, and a plurality of filamentary guides for said sheet material on at least one side of said path.
 2. The apparatus of claim 1, at least one of said conveying rolls being driven.
 3. The apparatus of claim 2, said filamentary guides having a diameter of no more than 0.10 inch.
 4. The apparatus of claim 3, said filamentary guides being substantially parallel to said path.
 5. The apparatus of claim 4, at least one of said conveying rolls having a plurality of circumferential grooves at spaced intervals along its length, said filamentary guides passing through the portions of said grooves nearest said path.
 6. The apparatus of claim 5, said first and second conveying rolls being located at spaced intervals throughout the length of said path.
 7. The apparatus of claim 6, the filamentary guides having surfaces of polymeric material, being connected to spring tensioning means, and being located in two planes that are parallel to each other and to said path and are no more than 0.5 inch apart, one of said planes being on the bottom of said path, the other of said planes being on the top of said path.
 8. The apparatus of claim 7 having at least one pair of coacting drive rolls, at least one of which has a surface of resilient polymeric material.
 9. The apparatus of claim 8, said nozzles having three frusto-conical sections, the section of smallest diameter being located at the discharge end of the nozzle and having a wall taper of not more than 4*, the intermediate section having a wall taper of 15*-20*, and the largest section being located at the base of the nozzle and having a wall taper of not more than 4*.
 10. The apparatus of claim 3, said conveying rolls comprising two pairs of coacting drive rolls, one pair being located at the entrance of said drying chamber, the other pair being located at the exit of said drying chamber.
 11. The apparatus of claim 10, at least one of said drive rolls having circumferential grooves at spaced intervals along its length, said filamentary guides being parallel to said path and passing through the portions of said grooves nearest said path.
 12. The apparatus of claim 11, the filamentary guides having surfaces of polymeric material, being connected to spring tensioning means, and being located in two planes that are parallel to each other and to said path and are no more than 0.5 inch apart, one of said planes being on the bottom of said path, the other of said planes being on the top of said path.
 13. The apparatus of claim 12, at least one of said coacting drive rolls having a surface of resilient, polymeric material. 